CAS E REP O R T Open Access Serous papillary adenocarcinoma possibly related to the presence of primitive oocyte-like cells in the adult ovarian surface epithelium: a case report Irma Virant-Klun 1* , Thomas Skutella 2 , Branko Cvjeticanin 1 , Martin Stimpfel 1 and Jasna Sinkovec 1 Abstract Introduction: The presence of oocytes in the ovarian surface epithelium has already been confirmed in the fetal ovaries. We report the presence of SSEA-4, SOX-2, VASA and ZP2-positive primitive oocyte-like cells in the adult ovarian surface epithelium of a patient with serous papillary adenocarcinoma. Case presentation: Ovarian tissue was surgically retrieved from a 67-year old patient. Histological analysis revealed serous papillary adenocarcinoma. A proportion of ovarian cortex sections was deparaffinized and immunohistochemically stained for the expression of markers of pluripotency SSEA-4 and SOX-2 and oocyte- specific markers VASA and ZP2. The analysis confirmed the presence of round, SSEA-4, SOX-2, VASA and ZP2- positive primitive oocyte-like cells in the ovarian surface epithelium. These cells were possibly related to the necrotic malignant tissue. Conclusion: Primitive oocyte-like cells present in the adult ovarian surface epithelium persisting probably from the fetal period of life or developed from putative stem cells are a pathological condition which is not observed in healthy adult ovaries, and might be related to serous papillary adenocarcinoma manifestation in the adult ovarian surface epithelium. This observation needs attention to be further investigated. Keywords: human, oocytes, ovarian surface epithelium, serous adenocarcinoma Introduction In fetal ovaries, the number of germ cells reaches a peak of ~6 to 7 million during the fifth month post-fertiliza- tion [1], after which germ cell reduction occurs during prenatal development, resulting in the presence of only 1 million of female germ cells before birth. Two mechanisms have been proposed to restrict the pool of female gametes during prenatal life: 1) germ cell degen- eration inside the developing ovary and, 2) germ cell extension into the ovarian surface epithelium and exfo- liation from the ov arian surface into th e coelomic cavity [1-7]. Therefore, primitive oocytes can be found in the ovarian surface epithelium and on the surface of fetal ovaries, as revealed by the t ransmission and scanning electron microscopy. Germ cells may reach the site of ovarian surface epithelium by still retained amoeboid movements in early developmental stages, or are pas- sively pushed there by the morphogenetic rearrange- ment of somat ic cells in later stages of ovarian development. This phenomenon is observed in human fetal ovaries, might persist until the puberty, but is not present in adult ovaries. It has already been proposed that these residual primitive oocytes in the adult ovarian surface epithelium may give rise to abnormal cell growth, such as teratomas [1,2], but not much experi- mental evidence has been available. Recent findings have confirmed the presence of puta- tive stem cells in the adult human ovarian surface epithelium [8-10]; they can also be found in the ovaries of older women [9,11]. Putative stem cells are small * Correspondence: irma.virant@gmail.com 1 Department of Obstetrics and Gynecology, University Medical Centre Ljubljana, Slovenia Full list of author information is available at the end of the article Virant-Klun et al. Journal of Ovarian Research 2011, 4:13 http://www.ovarianresearch.com/content/4/1/13 © 2011 Virant-Klun et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, di stribution, and reproduction in any medium, provided the original work is properly cited. round cells with diameters of 2 to 4 μmthatexpress some markers of plu ripotent stem cells and can develop in vitro into primitive oocyte-like cells. Putative stem cells found in adul t ovarian surface epithelium resemble very small embryonic-like stem cells (VSELs) found in other adult tissues and o rgans [12-14]. It is proposed that VSELs originate in the epiblast and persist in adult tissues and organs from the embryonic period of life [15]. Case report Ovarian tissue was surgically retrieved from a 67-year old patient. It was paraffin embedded, cut into sections, histologically analysed, and serous papillary adenocarci- noma was diagnosed. After he matoxylin-eosin staining some corpora albicans, atretic follicles, small inclusion cysts, and rete ovarii were observed. Randomly, a pro- portion of ovarian cortex sections was deparaffinized and immunohistochemically stained for the expression of SSEA-4 (FITC-conjugated antibodies) and SOX-2 (PE-conjugated antibodies), the markers of pluripotency, to search for the presence of putative stem cells. The analysis confirmed the presence of round, SSEA-4 and SOX-2-positive primitive oocyte-like cells in the ovarian surface epithelium. These cells resembled primitive oocytes in the ovarian surface epithelium of fetal ovaries (Figure 1). If not primitive oocytes, these cells might be oogonia or stem cells expressing markers of pluripo- tency. They were round, morphologically resembled pri- mitive oocytes with diameters from 10 t o 15 μm, and Figure 1 Primitive oocytes (arrows) in the ovaries of a 15 week-old fetus histologically analyzed at our department. (A, B) In the ovarian surface epithelium (light microscopy, magnification 1000×). (C) Just below the ovarian surface epithelium (light microscopy, magnification 1000×). Figure 2 Primitive oocyte-like cells (arrows) in the ovarian surface epithelium above the autofluorescent necrotic malignant tissue of a patient with serous papillary adenocarcinoma. (A, D) SSEA-4-positive cells (green). (B, E) SOX-2- positive cells (red). (C, F) Non-stained cells. (A, B, C: fluorescent and light microscopy, magnifications 400×; D, E, F: fluorescence and light microscopy, magnifications 1000×). Virant-Klun et al. Journal of Ovarian Research 2011, 4:13 http://www.ovarianresearch.com/content/4/1/13 Page 2 of 5 were present in empty places looking like “chambers” among epithelial cells (Figures 2 and 3) quite compar- able to fetal ovaries before the formation of follicles (Figure 1). Ad ditional immunohistochemistry revealed that a proportion of these cells was positively stained on the oocyte-specific ma rkers VASA (Figure 4) and ZP2 (Figure 5). More detailed observation revealed two populations o f these cells: smaller ones with diameters of up to 5 μm (Figures 4A, B and 5B, F) resembling VSELs and bigger ones with diameters of around 10 μm (Figures 4, 5). VASA staining a lso confirmed the pre- sence of rare positively stained bigger round cells with diameters of up to 30 μm in the ovarian cortex bellow the ovarian surface epithelium (Figure 4G, H). These cells were not present in follicles like normally in women of reproductive age, but were appearing as indi- vidual cells integrated in the ovarian cortical tissue. Primitive oocyte-like cells were mostly present near the autofluorescent necrotic malignant tissue. At some places it was clearly seen that primitive oocyte -like cells were released from their “chambers ” in the ovar- ian surface epithelium and started to change into hypertrophic/necrotic cells (Figures 3 and 6) and further into autofluorescent necrotic malignant tissue, which protruded deeper into the ovarian cortex. The nuclei of hypertrophic/necrotic cells consisted of degraded chromatin as revealed by DAPI staining (Figure 6C). This type of cells is usually not present in the healthy adult human ovarian surface epithelium. Discussion Serous adenocarcinoma is a type of epithelial ovarian can- cer, which is the most common among ovarian cancers. Ovarian cancers account f or 6 p ercent of a ll cancers among women according to the American Cancer Society. The five-year survival rate in women with advanced ovarian cancer is 15 to 20 percent, but if the disease is found at an earl y stage, survival approaches 90 percent [16]. Women with a personal/family history of ovarian or other cancers are at the highest risk of having ovarian serous carcinoma, especially if their mother or sister had ovarian cancer. Other risk factors include: increased age, use of high-dose estrogens without progesterone for a long period, uninter- rupted ovulation due to infertility, no pregnancies, no use Figure 3 Normal and hypertrophic primitive oocyte-like c ells (arrows) in the ovarian surface epithelium above the autofluorescent necrotic malignant tissue of a patient with serous papillary adenocarcinoma. (A, D) SSEA-4-positive cells (green). (B, E) SOX-2-positive cells (red). (C, F) Non-stained cells. (fluorescence and light microscopy, magnifications 400×). Legend:h- hypertrophic/necrotic cells. Figure 4 VASA-positive cells (arrows) in the ovarian surface epithelium and cortex. (A, B) Smaller cells with diameters of 2 to 4 μm in the epithelium. (C-F) Bigger cells with diameters of 10 μm in the epithelium. (G, H) Rare cells with diameters of approximately 30 μm in the cortex. (light microscopy, magnifications 400× and 1000×). Legend: blue-positive cells (Peroxidase/True Blue). Scale bar: 100 μm. Virant-Klun et al. Journal of Ovarian Research 2011, 4:13 http://www.ovarianresearch.com/content/4/1/13 Page 3 of 5 of birth control, and defects in the BRCA1 or BRCA2 genes. Unfortunately, in most women ovarian serous carci- noma is not diagnosed until the disease is advanced, and has spread into the abdomen or beyond due to non-clear physical symptoms. Therefore, early diagnosis is very important. Here we report the p resence of primitive oocyte-like cells in t he adult h um an ovarian surf ace epithe- lium as related to epithelial ovarian cancer. These cells resembled primitive oocytes in the ovarian surface epithe- lium of fetal ovaries, and might have been involved in the manifestation of serous papillary adenoca rcinoma in thi s patient. They expressed the analyzed markers of pluripo- tency SSEA-4 and SOX-2 and oocyte-specific markers VASA and ZP2 (glycoprotein of zona pellucida), therefore, the germline character of these cells is quite possible. The primitive oocyte-like cells in the ovarian surface epithelium of thi s patient mig ht have persisted from the fetal period of life o r developed from the putative s tem cells in the o varian surface epithelium. They might present a pathological state leading to the manifestation of o varian serous papillary ade- nocarcinoma. It has been confirmed that teratoma and other germ cell tumors can be formed from oocytes/ parthenogenetic embryos [17,18]. Similar primitive oocyte- like cells as reported here have already been described in the adult ovarian surface epithelium in a mouse model; ovarian surface epithelium of adult mouse ov aries seems to possess rare premeiotic germ cells that can generate oocytes following transplantation into a young host envir- onment [19], but to our knowledge there has been no evi- dence in humans u ntil now. Conclusion Primitive oocyte-like cells present in the adult ovarian surface epithelium of the postmenopausal patient that probably persisted from the fetal period of life or had developed from putative stem cel ls in the ovarian sur- face epithelium are a pathological condition and might be related to serous papillary adenocarcinoma manifes- tation in this patient. This observation needs attention to be further investigated. Consent statement Written informed consent was obtained from the patient for publication of this case report and accompanying images. Abbreviations FITC: Fluorescein Isothiocyanate; PE: Phycoerythrin; SSEA-4: Stage Specific Embryonic Antigen-4; SOX-2: SRY-related HMG-box-2. Acknowledgements We acknowledge Prof. Peter Dovc, Biotechnical Faculty, University of Ljubljana, who kindly provided us the anti-goat secondary antibodies to analyze oocyte-specific markers VASA and ZP2 by immunohistochemistry and Ms. Mojca Pirc, B.A., for revision of the English language. We also greatly Figure 5 ZP2-positive cells (arrows) in the ovarian surface epithelium. (A-F) Bigger cells with diameters of approximately 10 μm. (B, F) Also smaller cells with diameters of approximately 5 μm. (G, H) Negative controls. (light microscopy, magnifications 400× and 1000×). Legend: brown-positive cells (Peroxidase/DAB). Scale bar: 100 μm. Figure 6 Autofluorescent necrotic malignant tissue with clearly visible hypertrophic primitive oocyte-like cells (arrows) releasing from their “chambers”. (A) Stained for the expression of SSEA-4, marker (green) of pluripotency. (B) Stained for the expression of SOX-2, marker (red) of pluripotency. (C) After DAPI (blue) staining. (D) Non-stained. (fluorescence and light microscopy, magnifications 400×). Legend: h-hypertrophic/necrotic cells. Virant-Klun et al. Journal of Ovarian Research 2011, 4:13 http://www.ovarianresearch.com/content/4/1/13 Page 4 of 5 acknowledge the Slovenian Research Agency (ARRS, grant J3-0415/Irma Virant-Klun) and German Federal Ministry of Education and Research (BMBF, grant 01GN1001/Thomas Skutella) for the financial support. Author details 1 Department of Obstetrics and Gynecology, University Medical Centre Ljubljana, Slovenia. 2 Institute for Anatomy and Cell Biology, Faculty of Medicine, University of Heidelberg, Heidelberg, Germany. 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Aging (Albany NY) 2009, 1:971-8. doi:10.1186/1757-2215-4-13 Cite this article as: Virant-Klun et al.: Serous papillary adenocarcinoma possibly related to the presence of primitive oocyte-like cells in the adult ovarian surface epithelium: a case report. Journal of Ovarian Research 2011 4:13. Submit your next manuscript to BioMed Central and take full advantage of: • Convenient online submission • Thorough peer review • No space constraints or color figure charges • Immediate publication on acceptance • Inclusion in PubMed, CAS, Scopus and Google Scholar • Research which is freely available for redistribution Submit your manuscript at www.biomedcentral.com/submit Virant-Klun et al. Journal of Ovarian Research 2011, 4:13 http://www.ovarianresearch.com/content/4/1/13 Page 5 of 5 . this article as: Virant-Klun et al.: Serous papillary adenocarcinoma possibly related to the presence of primitive oocyte-like cells in the adult ovarian surface epithelium: a case report. Journal. CAS E REP O R T Open Access Serous papillary adenocarcinoma possibly related to the presence of primitive oocyte-like cells in the adult ovarian surface epithelium: a case report Irma Virant-Klun 1* ,. observed in healthy adult ovaries, and might be related to serous papillary adenocarcinoma manifestation in the adult ovarian surface epithelium. This observation needs attention to be further investigated. Keywords: